Do you think it is necessary to give tips or it is just a tradition that is required?
It's not actually required or necessary because in the first place it is your money that you bet and if you lose they don't give you cashback in real casinos and tipping them is like showing thanks for the profit you have earned from them.
Giving tips will always depend on their service and the profit that you have made, though sometimes Im not giving any tips even if I won simply because they didnt do anything to help me at all so I dont think they deserve to get it, if they are very helpful with you then this is the only time I will give a tip. This is not a requirement though, giving tip should always came from your own willingness and not just because someone forced you to do so.